Wear compensating apparatus having plural pawls



Dec. 21, 965 J. B. ODANIEL ETAL 3,224,546

WEAR COMPENSATING APPARATUS HAVING PLURAL PAWLS 2 Sheets-Sheet 1 Filed Jan. 30, 1964 INVENTORS. JEROME B. '0" DANIEL LEON E. PALMER QMQD.

ATTORNEY.

1965 J. B. ODANIEL ETAL 3,

WEAR COMPENSATING APPARATUS HAVING PLURAL PAWLS 2 Sheets-Sheet 2 Filed Jan. 30, 1964 FIG. 2

United States Patent 3,224,546 WEAR CUMPENSATHNG APPARATUS HAVING PLURAL PAWLS Jerome B. UDaniel and Leon E. Pairner, Lexington, Ky,

assignors to International Business Machines Corporation, New York, N.Y., a corporation of New York lFiied 52m. 30, 1964, Ser. No. 341,245 7 Claims. (Cl. 19'7-16) The present invention relates generally to the mechanical arts and more particularly to apparatus which automatically compensates for wear in mechanisms that move a driven member to different positions, such as the mechanisms employed to move a print element of a typewriter.

In US. Patent 2,919,602, issued to L. E. Palmer and which is assigned to the assignee of the present invention, there is shown a typewriter having a single print element that is movable to different positions for bringing any one of various characters to a printing position. The print element has the general shape of a truncated spheroid and the mechanisms for moving the print element comprise means for rotating the print element in either direction from a home position. A detenting means, such as the type disclosed in US. Patent 2,926,768, issued to L. E. Palmer et al. and which is also assigned to the assignee of the present invention, is employed for accurately locating the print element in each of its printing positions. This detenting means will compensate for slight inaccuracies in adjustment of the mechanisms for moving the print element and for slight wear in their operating parts. If nothing more is provided, a manual adjustment of the mechanisms becomes necessary as soon as the inaccuracies in the mechanisms and the wear in their operating parts exceed the compensation that may be obtained from the detenting means.

The above problem has been recognized in the art and it has previously been proposed to provide a wear compensating device which will automatically compensate for a portion of the wear in the mechanisms to obtain a longer period of operation before manual adjustment is necessary. Such a device, as shown in US. Patent 2,989,- 166, issued to G. A. Walker et al. and assigned to the assignee of the present invention, comprises a pair of arms carrying a pulley about which tape passes. One end of the tape is connected to a pulley fixed on a spindie carrying the print element. A spring tends to rotate the latter pulley for maintaining a tension on the tape. Formed in the arms are vertical slots carrying a roller which is held against a lever by the action of the tape on the arms. During a compensating action, the lever is caused to move slightly relative to the arms and this permits the roller to move to a lower position in the slots. if the tension on the tape is inadvertently removed at any time, the arms may move relative to the lever and permit the roller to drop, thereby causing the setting of the device to become inaccurate. A removal of the tension on the tape may take place in many Ways, such as when the print element is being removed or replaced from the spindle by the typist. By providing a clamping member which is held by a spring against the roller at all times except when the compensating device is in a position to make an error correction, an inadvertent movement of the roller in the slots is prevented. This latter arrangement is disclosed in US. Patent 3,133,620, issued to S. A. Okcuoglu et al. and which is also assigned to the assignee of the present invention.

The above described wear compensating device has been found well adapted for the purposes intended and has been extensively employed. However, it is desirable to compensate for a greater portion of the inaccuracies 3,224,546 Patented Dec. 21, 1965 or Wear in the mechanisms or parts, such as at least a portion of the wear in the case shift mechanism operat ing on the tape and changes in the eifective length of the tape itself. Further, the wear compensating apparatus should be relatively simple in construction and operation, being formed from a small number of uncomplicated parts.

Briefly, the present invention relates to improved wear compensating apparatus comprising a clutch means interconnecting a driven member and a movable member. The clutch means is normally operative to drivingly interconnect the driven and movable members so that they move together. However, when at least one preselected position is reached, the clutch means is released and biasing means is effective to cause relative movement between the members as is necessary to compensate for wear and the like. In the illustrated embodiment of the invention, the clutch means takes the form of a dual pawl clutch having a pair of pawls mounted from the movable member which engage a toothed flange on the yieldably biased driven member. The driven member is a pulley having a tape attached thereto. The tape is pulled and released to cause rotational movements of the driven and movable members. One of the pawls engages a relatively fixed stop and is released when the preselected position is reached to permit the compensating operation.

t is the primary or ultimate object of the invention to provide improved wear compensating apparatus which automatically adjusts itself to compensate for at least a portion of the wear in the mechanisms employed for moving a driven member to different positions.

Another object of the invention is the provision of wear compensating apparatus which is effective to automatically compensate for a greater portion of the wear in the mechanisms employed to rotate a print element of a typewriter than it has heretofore been possible to automatically compensate. The wear compensating apparatus is located at the base of the spindle mounting the print element whereby a greater portion of the inaccuracies and wear in the various mechanisms acting on or guiding the tape or changes in the effective length of the tape are compensated. A significantly longer period of typewriter operation is obtained before manual adjustment is necessary.

A further object of the invention is the provision of wear compensating apparatus which is operative to compensate for wear only when the print element is in a preselected position. The arrangement is such that inadvertent removal of the tension from the tape while the print element is at rest will not produce incorrect operation of the wear compensating apparatus.

A still further object of the invention is the provision of wear compensating apparatus having the characteristics set forth above which is extremely compact and of simplified construction whereby the same can be manufactured at a low cost but yet is very rugged and highly reliable in operation.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in that accompanying drawings.

In the drawings:

FIGURE 1 is a front view of printing mechanism embodying improved wear compensating apparatus constructed and operated in accordance with the teachings of the present inevntion;

FIGUURE 2 is a perspective view of a print element and means for rotating it from a home position;

FIGURE 3 is a plan sectional view taken along the section line 33 of FIGURE 2; and

590 Madison Avenue, New York 22, New York.

A print element 11 having the general shape of a truncated spheroid is detachably and removably secured to the upper end of a spindle 12. Formed about the periphery of the print element 11 in generally vertically spaced and circumferentially extending rows are a plurality of characters 13. Mechanisms are provided for rotating and tilting the print element 11 to bring any selected character to a printing position in front of a printing platen 14. The print element is then thrown forward toward the printing platen 14 to effect printing of the selected character.

The spindle 12 is mounted for rotation in either direction on a rocker plate 16 .and is connected at its lower end to a rotate pulley 17 by the wear compensating apparatus as will be further described. The rotate pulley 17 has a relatively large diameter and a groove 18 is formed about its outer periphery. As most clearly shown in FIGURE 4 of the drawings, rotate pulley 17 comprises a depending annular hub 19 which is connected to the inner end of a coil spring 21. The coil spring is of the mainspring type and is nestingly received in a cup shaped spring cage 22 to which the outer end of the spring is attached. The spring cage is rigidly mounted from the rocker plate 16. The convolutions of the coil spring 21 are wound in such a direction that the rotate pulley 17, spindle 12 and print element 11 are all biased for rotation in a clockwise direction as is indicated by arrows 24.

The rotate pulley 17 has a slot 25 therein and firmly secured in this slot by any convenient clamping means is one end of a thin and flexible rotate tape 26. The rotate tape 26 is received in the peripheral groove 18 of the rotate pulley 17 and, after making slightly less than two complete revolutions of the rotate pulley, extends longitudinally to a pulley 28 rotably mounted at the upper end of a rotate arm 29. The rotate arm 29 is located at the left side of the printing mechanism as viewed in FIG- URES l and 2 of the drawings. After passing about the pulley 28, the rotate tape 26 extends longitudinally across the printing mechanism to a case shift pulley 30 mounted for rotation on the upper end of a case shift lever 31. Case shift lever 31 is located at the right side of the printing mechanism. The other end of the rotate tape 26 .is connected to a stud 32 which extends from a carrier 33.

The carrier 33 (see FIGURE 1 of the drawings) is guided for longitudinal movement in front of the printing platen 14. Escapement and carriage return apparatus, not shown, are provided to cause longitudinal movement of the carriage. The rocker plate 16 is pivoted to the carrier 33 by rocker shaft 34 so that the rocker plate 16 and the print element 11 can be thrown forward by print apparatus, not shown, to effect printing. The mounting of rotate tape 26 is such that as long as the rotate arm 29 and case shift arm 31 remain in fixed positions, the print element 11 will retain the same rotational position regardless of the longitudinal position of the carrier 33, rocker plate 16 and the print element 11 with respect to the printing platen 14. However, movement of either the rotate arm 29 or the case shift arm 31 will cause rotational movement of the print element.

The rotate arm 29 is pivotally mounted intermediate its ends by pin 35 and is connected at its lower end to a rotate link 36. The other end of rotate link 36 is attached to one arm of a rotate bellcrank 37 which is supported at 38 and whose other arm is connected to a balance lever 39 form-ing part of rotate selection mechanism generally designated by reference numeral 40. Included In the rotate selection mechanism are selecting links 41 and 42 which are hook shaped at their lower ends and are connected at their upper ends to a floating member 43 in such a way they may swing forwardly relative to the floating member and also permit pivotal movement about the latter in either direction. A link 45 pivotally connects floating member 43 "to one end of another floating member 46 which is connected by a link 47 to one end of balance lever 39. Another selecting link 48 is connected to the opposite end of floating member 46 and has a hook shaped portion at its lower end. The other end of balance lever 39 is pivotally connected to a link 49 which is normally held in the position shown but may be moved vertically a predetermined distance to a higher position.

During a character selection operation, one or more of the selecting links 41, 42 and 48 are swung forwardly to position their hooked portions under a bail 50 which is caused to rock downwardly. The connections between the floating members 43 and 46 and the links 45 and 47 are such that a movement of the selecting link 41 downwardly with the bail 50 causes the rotate bellcrank 37 to rotate one unit in a counterclockwise direction. Movement of either selecting link 42 or selecting link 48 downwardly with the bail 50 causes the bellcrank 37 to rotate two units in a counterclockwise direction. When two or more selecting links are moved with the hail, the rotate bellcrank rocks a distance equal to the sum of the distances obtained by movement of the individual selecting links. As the rotate bellcrank 37 rocks counterclockwise, the rotate arm 29 pivots and pulls on the tape 26 to cause a rotation of the print element 11 in a counterclockwise direction. A rocking of the bellcrank 37 one unit distance causes counterclockwise turning of the print element 11 by a distance equal to the spacing between adjacent vertical rows of the characters formed on the print element.

The coil spring 21 acting on the print element 11 maintains a tension on tape 26 and tends to swing the upper end of rotate arm 29 to the right from the position shown in FIGURES l and 2 of the drawings. This places a tension on rotate link 36 tending to rotate the bellcrank 37 in a clockwise direction. Bellcrank 37, acting through balance lever 39, tends to raise the link 49 from the position shown. Link 49 is normally latched in its lower position but may be unlatched so it follows a cam, not shown, to move to its raised position. When the link 49 is moved to its raised position, the rotate bellcrank 37 rocks clockwise a distance of five units, the pulley 28 moves to the right and the print element 11 turns clockwise by a distance corresponding to five units. If the selecting links 41, 42 and 48 are actuated simultaneously with the lifting of link 49, the rotate bellcrank 37 rocks clockwise a distance corresponding to five units minus the counterclockwise distance obtained by operating the selecting links. From the above discussion, it is apparent the print element 11 may be turned in both clockwise and counterclockwise directions from a home position by any distance from one to five units upon proper actuation of the selecation mechanism 40. The rotate selection mechanism is actuated in response to depression of keylever by a typist or by received signals controlling the operation of solenoids, not shown, as is well known.

The case shift arm 31 mounted at the right of the printing mechanism carries a cam follower roll 52 intermediate its end which engages a case shift cam 53. The case shift cam 53 is rotated in response to case shift signals and causes pivotal movement of the case shift arm about pivot point 54. Lower case characters are formed on one half of the print element and upper case characters are formed on the other half thereof. Clockwise pivotal movement of the case shift arm 31 from the position illustrated in FIGURE 2 of the drawings causes the print element to rotate in a counterclockwise direction through 180 degrees. Upper case characters are then selected for printing upon actuation of the selection mechanism 40. When the case shifting mechanism is not actuated, lower case characters are brought to the printing position upon operation of the selection mechanism. This case shifting mechanism is fully disclosed in the above referenced Patent 2,919,002 and the instruction manual.

Any portion of the selection or case shift mechanisms which wears or moves out of adjustment will cause the print element to rotate to a position which is spaced from the desired position during a character selection operation. This will cause the print element to be displaced slightly so the selected characters are offset from the correct printing position. While detenting means as shown in Patent 2,926,768 is employed to correct slight positioning errors, the inaccuracies and wear in the mechanisms may exceed the correcting ability of the detenting means on at least a portion of the selection operations. The wear compensating apparatus is designed to compensate for at least a portion of the inaccuracies and wear in the mechanisms for rotating the print element when the latter is rotated clockwise by five units and the case shift mechanism has not been actuated.

As shown in FIGURES 3 and 4 of the drawings, the rotate pulley 17 has a vertically extending shoulder 55 which extends for slightly more than 180 degrees about the periphery of this pulley. Milled or otherwise formed on the inner face of the shoulder 55 are teeth 56 which preferably are very fine and closely spaced and define a ratchet means. A pair of pawls 57 and 58 are pivotally mounted intermediate their ends by pins 59 and 60 to the oppositely projecting arms 61 of an annular hub 62. The hub 62 is rigidly attached to the spindle 12 by a set screw 64 or other convenient attachment means. One end of each of the pawls has teeth 65 formed thereon and is adapted to engage the teeth 56 on shoulder 55 of the rotate pulley. The opposite ends of the pawls 57 and 58 are spanned by a tension spring 66 which exerts a force that normally causes the knurled or toothed ends of the pawls to engage the teeth 56 on the rotate pulley. When the pawls 57 and 58 engage the teeth on the rotate pulley, a rigid drive connection is provided between the rotate pulley 17 and spindle 12. The print element 11 moves in both rotational directions with the rotate pulley in response to movements imparted to the tape 26 by the rotate selection and case shift mechanisms.

A stop plate 67 is adjustably mounted on the rocker plate 16 in relatively fixed relation with respect to the rotational movements of the rotate pulley 17 and the print element 11. A stud 68 extends vertically from the rear end of the pawl 58 and, as will be later explained, is adapted to engage the stop plate 67 when the print element moves clockwise by five units as a lower case character is selected. A vertically extending tab 69 is formed integral on the arm 61 of the hub 62 associated with the pawl 58 and defines a pawl stop.

Initially, the stop plate 67 is adjusted so the stud 68 engages the same and pawl 58 is pivoted out of engagement with the teeth 56 on the shoulder 55 and against tab 69 when the print element has rotated five units clockwise and the case shift mechanism has not been actuated. As the machine is used, wear and changes in the adjustment of any part or portion of the rotate selection mechanism or the case shift mechanism allow the coil spring 21 to move the rotate pulley 17 more and more in the clockwise direction during at least a portion of the selection operations. Under such wearing conditions, the pawl 58 is released when a clockwise rotation of five units is selected and the case shift mechanism is not actuated to disengage the rotate pulley 17 from the print element 11. The print element remains in its proper printing position at this time but the rotate pulley continues to rotate clockwise due to the force exerted by the coil spring 21 until all slack in the rotate tape 26 has been taken up. The pawl 58 engages pawl stop 69 and this sets up reactive forces which cause pawl 57 to ratchet or move with respect to the teeth 56 on shoulder 'of the rotate pulley. As the selection mechanism 40 is de-energized and the rotate pulley begins to rotate counterclockwise from the selected position toward the home position, the pawl 58 drops into the teeth 56 on the rotate pulley at a new position. The print element 11 is returned to the home position and an automatic adjustment operation to compensate for a major portion of the wear is completed. In essence, the wear compensating apparatus comprises a dual pawl clutch operative to transmit movement to the spindle and print element in both rotational directions until the pawl 58 is released. A clutch of this general type is disclosed in co-pending patent application Serial No. 312,135, filed September 27, 1963, in the names of George A. Walker and Richard E. Hosey which is assigned to the assignee of the present invention.

The rotate pulley 17 and the print element 11 are drivingly connected at all times except occasionally during the middle of a particular selection cycle. The arrangement is such that external rotational forces exerted on the print element 11 or spindle 12, such as may occur when the print element is removed or replaced, do not alter or change the adjusted positional relation between the spindle 12 and the rotate pulley 17. The shoulder 55 and the teeth 56 do not extend completely around the periphery of the rotate pulley since it is usually only necessary to compensate for considerably less than one fourth of a revolution of the rotate pulley over the life of the printing mechanism. Also, the adjustable stop plate 67 does not interfere with selection or case shift operations since slightly less than one complete revolution of the print element is required to position any selected character in the printing position.

As mentioned above, characters are formed in vertically spaced circumferentially extending rows on the print element. The printing mechanism comprises mechanism for tilting the print element in response to character selection signals to select a circumferentially extending row of characters. This tilt selection mechanism has not been described or particularly shown in the present disclosure but is fully explained in the aboveidentified Patent 2,919,002 and instruction manual. If desired, wear compensating apparatus of type herein described can be incorporated in this tilt selection mechanism.

It should now be apparent that the objects initially set forth have been accomplished. Of particular importance is the provision of Wear compensating apparatus which automatically compensates for a major portion of the inaccuracies and wear in mechanisms employed for positioning a driven member and which apparatus is highly simplified in construction and operation. The teachings of the present invention, while being particularly applicable to printing mechanisms of the type described, can be employed in other systems where wear is encountered in mechanisms adapted to position a movable member.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. Apparatus for compensating for wear and the like in at least one mechanism operable to control movement of a print member having spaced characters thereon to selectively position the characters at a printing position comprising:

a print member having a plurality of spaced characters mounted about the periphery thereof;

a rotatable member and mechanism interconnected with said rotatable member, operable to cause movement of said rotatable member;

clutch means drivingly interconnecting said rotatable member and said print member;

said clutch means operable when engaged to cause oscillatory movement of said print member with said rotatable member in both rotational direct-ions through a printing position;

means to rel-ease said clutch means each time said rotatable member and said print member are in at least one preselected rotational position to position an associated one of said characters at said printing position; and

means connected with one of said members operable to effect relative movement between said members when said clutch means is released to automatically compensate for wear and the like in said mechanism.

2. Apparatus according to claim 1 further characterized by:

said rotatable member comprises a rotate pulley;

a flexible rotate tape attached to and extending at least partially around said rotate pulley;

said connected means being attached to said rot-ate pulley and biasing the same for movement in one rotational direction;

said mechanism being operable to release and pull on said tape to cause rotation of said rotate pulley in both rotational directions by permitting winding of said tape on said rotate pulley in one rotational direction and causing unwinding of said tape in the other rotational direction; and

said preselected rotational position being in said one rotational direction.

3. Apparatus for compensating for wear and the like in at least one mechanism operable to control movement of a print element having spaced characters thereon to selectively position the characters at a printing position comprising:

a print element having a plurality of spaced characters mounted about the periphery thereof;

a spindle mounting said print element for rotational movements in both rotational directions;

a rotate pulley mounted for rotation;

means biasing said rotate pulley for movement in one rotational direction;

a flexible rotate tape attached to and extending at least partially about said rotate pulley;

at least one mechanism operating on said tape to pull and release the same 'to cause rotation of said rotate pulley;

a bi-directional clutch means interconnecting said rotate pulley and said spindle so that oscillatory rotational movements of said rotate pulley causes like oscillatory movements of said print element through a printing position when said clutch means is engaged; and

means to release said clutch means each time said rotate pulley is in at lea-st one predetermined rotational position in said one rotational direction to position an associated one of said characters at said printing position to permit independent movement of said rotate pulley with respect to said spindle under the action of said biasing means as necessary to automatically compensate for wear and the like in said mechanism.

4. Apparatus for compensating for wear and the like in at least one mechanism operable to control movement of a print member having spaced characters thereon to selectively position the characters at a printing position comprising:

a print member having a plurality of spaced characters mounted thereon;

a driven member and mechanism interconnected with said driven member operable to cause movement of said driven member in either of at least two directions;

8 said driven member and said print member being mounted for oscillatory movement about a common axis; clutch means drivingly interconnecting said driven memher and said print member for oscillatory movement through a printing position to a number of preselected positions when said clutch is engaged; means to release said clutch means each time said driven member and said print member are in at least one of said preselected positions to position an as- 10 sociated one of said characters at said printing position; and

means connected with one of said members operable to effect relative movement between said members when said clutch means is released to automatically compensate for wear and the like in said mechanism.

5. Apparatus for compensating for wear and the like in at least one mechanism operable to control movement of a print element comprising:

a print element having a plurality of spaced characters mounted about the periphery thereof;

a spindle mounting said print element for rotational movements in both rotational directions;

a rotate pulley mounted for rotation;

means biasing said rotate pulley for movement in one rotational direction;

a flexible rotate tape attached to and extending at least partially about said rotate pulley;

at least one mechanism operating on said tape to pull and release the same to cause rotation of said rotate p l y;

a bi-directional clutch means interconnecting said rotate pulley and said spindle whereby rotational movements of said rotate pulley causes like rotational movements of said print element when said clutch means is engaged;

means to release said clutch means when said rotate pulley is in at least one predetermined rotational position in said one rotational direction to permit independent movement of said rotate pulley with respect to said spindle under the action of said biasing means as necessary to automatically compensate for wear and the like in said mechanism;

said clutch means comprising a circumferentially extending flange on said rot-ate pulley;

an annular hub member rigidly attached to said spindle and having a pair of projecting .arms;

a pair of pawls each pivo-tally attached to one of said arms intermediate its ends;

one set of ends of said pawls adapted to engage said flange; and

means biasing said one set of ends of said pawls into engagement with said flange.

b 6. Apparatus according to claim 5 further characterized said means to release comprises a stop surface mounted in relatively fixed relation with respect to said rotate pulley and engageable by one of said pawls to pivot the same from engagement with said flange of said rotate pulley.

b 7. Apparatus according to claim 6 further characterized a stop member carried by the arm of said hub associated with said one of said pawls; and

said stop member limiting pivotal movement of said one of saidpawls when the latter engages said stop surface during a wear compensating operation.

References Cited by the Examiner UNITED STATES PATENTS 5/1932 Lyman 1921l1 X 10/ 1944 Almen. 2,989,166 6/1961 Walker et a1 197-16 3,133,620 5/1964 Okcuoglu et al. 197l6 75 ROBERT E. PUL'FREY, Primary Examiner. 

1. APPARATUS FOR COMPENSATING FOR WEAR AND THE LIKE IN AT LEAST ONE MECHANISM OPERABLE TO CONTROL MOVEMENT OF A PRINT MEMBER HAVING SPACED CHARACTERS THEREON ON SELECTIVELY POSITION THE CHARACTERS AT A PRINTING POSITION COMPRISING: A PRINT MEMBER HAVING A PLURALITY OF SPACED CHARACTERS MOUNTED ABOUT THE PERIPHERY THEREOF; A ROTATABLE MEMBER AND MECHANISM INTERCONNECTED WITH SAID ROTATABLE MEMBER, OPERABLE TO CAUSE MOVEMENT OF SAID ROTATABLE MEMBER; CLUTCH MEANS DRIVINGLY INTERCONNECTING SAID ROTATABLE MEMBER AND SAID PRINT MEMBER; SAID CLUTCH MEANS OPERABLE WHEN ENGAGED TO CAUSE OSCILLATORY MOVEMENT OF SAID PRINT MEMBER WITH SAID ROTATABLE MEMBER IN BOTH ROTATIONAL DIRECTIONS THROUGH A PRINTING POSITION; MEANS TO RRELEASE SAID CLUTCH MEANS EACH TIME SAID ROTATABLE MEMBER AND SAID PRINT MEMBER ARE IN AT LEAST ONE PRESELECTED ROTATIONAL POSITION TO POSITION AN ASSOCIATED ONE OF SAID CHARACTERS AT SAID PRINTING POSITION; AND MEANS CONNECTED WITH ONE OF SAID MEMBERS OPERABLE TO EFFECT RELATIVE MOVEMENT BETWEEN SAID MEMBERS WHEN SAID CLUTCH MEANS IS RELEASED TO AUTOMATICALLY COMPENSATE FOR WEAR AND THE LIKE IN SAID MECHANISM. 